feat(storage): add pinned field to issues schema

Add pinned column to the issues table to support persistent context markers
that should not be treated as work items (bd-7h5).

Changes:
- Add pinned column to schema.go CREATE TABLE
- Add migration 023_pinned_column.go for existing databases
- Update all issue queries to include pinned column
- Update scanIssues and scanIssuesWithDependencyType to handle pinned field
- Add Pinned field to types.Issue struct with JSON serialization
- Fix migrations_test.go to include pinned in legacy schema test

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/storage/sqlite/multirepo.go

@@ -261,6 +261,10 @@ func (s *SQLiteStorage) upsertIssueInTx(ctx context.Context, tx *sql.Tx, issue *
 	if issue.Ephemeral {
 		ephemeral = 1
 	}
+	pinned := 0
+	if issue.Pinned {
+		pinned = 1
+	}
 
 	if err == sql.ErrNoRows {
 		// Issue doesn't exist - insert it
@@ -270,8 +274,8 @@ func (s *SQLiteStorage) upsertIssueInTx(ctx context.Context, tx *sql.Tx, issue *
 				status, priority, issue_type, assignee, estimated_minutes,
 				created_at, updated_at, closed_at, external_ref, source_repo, close_reason,
 				deleted_at, deleted_by, delete_reason, original_type,
-				sender, ephemeral
-			) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+				sender, ephemeral, pinned
+			) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 		`,
 			issue.ID, issue.ContentHash, issue.Title, issue.Description, issue.Design,
 			issue.AcceptanceCriteria, issue.Notes, issue.Status,
@@ -279,7 +283,7 @@ func (s *SQLiteStorage) upsertIssueInTx(ctx context.Context, tx *sql.Tx, issue *
 			issue.EstimatedMinutes, issue.CreatedAt, issue.UpdatedAt,
 			issue.ClosedAt, issue.ExternalRef, issue.SourceRepo, issue.CloseReason,
 			issue.DeletedAt, issue.DeletedBy, issue.DeleteReason, issue.OriginalType,
-			issue.Sender, ephemeral,
+			issue.Sender, ephemeral, pinned,
 		)
 		if err != nil {
 			return fmt.Errorf("failed to insert issue: %w", err)
@@ -303,7 +307,7 @@ func (s *SQLiteStorage) upsertIssueInTx(ctx context.Context, tx *sql.Tx, issue *
 					issue_type = ?, assignee = ?, estimated_minutes = ?,
 					updated_at = ?, closed_at = ?, external_ref = ?, source_repo = ?,
 					deleted_at = ?, deleted_by = ?, delete_reason = ?, original_type = ?,
-					sender = ?, ephemeral = ?
+					sender = ?, ephemeral = ?, pinned = ?
 				WHERE id = ?
 			`,
 				issue.ContentHash, issue.Title, issue.Description, issue.Design,
@@ -311,7 +315,7 @@ func (s *SQLiteStorage) upsertIssueInTx(ctx context.Context, tx *sql.Tx, issue *
 				issue.IssueType, issue.Assignee, issue.EstimatedMinutes,
 				issue.UpdatedAt, issue.ClosedAt, issue.ExternalRef, issue.SourceRepo,
 				issue.DeletedAt, issue.DeletedBy, issue.DeleteReason, issue.OriginalType,
-				issue.Sender, ephemeral,
+				issue.Sender, ephemeral, pinned,
 				issue.ID,
 			)
 			if err != nil {